Ulnar nerve entrapment is a common condition where the ulnar nerve, one of the three main nerves in the arm, becomes compressed or irritated. This compression neuropathy is the second most frequently diagnosed in the upper extremity, occurring less often than carpal tunnel syndrome. The condition results from pressure or stretching of the nerve, causing symptoms in the hand and forearm. The specific site of entrapment dictates the nature of the symptoms a person experiences.
The Ulnar Nerve Pathway and Entrapment Locations
The ulnar nerve originates from the brachial plexus near the neck and travels down the arm to the hand. Its primary functions include providing sensation to the ring and pinky fingers, and controlling most of the small, intrinsic muscles responsible for fine hand movements and grip strength. Because the nerve runs close to the skin and bone in certain areas, it is susceptible to external pressure and injury.
The most frequent location for compression is at the elbow, a condition known as Cubital Tunnel Syndrome. Here, the nerve passes through a narrow space called the cubital tunnel, situated directly behind the bony bump on the inner side of the elbow, commonly referred to as the “funny bone.” Bending the elbow causes the nerve to stretch and the tunnel space to narrow, increasing pressure on the nerve significantly.
A less common site of compression occurs at the wrist, where the condition is called Guyon’s Canal Syndrome. Here, the ulnar nerve passes through Guyon’s canal, which is bordered by various ligaments and small bones. The nerve at this location divides into a superficial sensory branch and a deep motor branch. Entrapment can be caused by local trauma, cysts, or repetitive pressure, such as that experienced by cyclists leaning on handlebars.
Identifying the Symptoms and Contributing Factors
Symptoms of ulnar nerve entrapment generally begin with sensory changes, often described as “pins and needles” or numbness. These sensations are felt in the pinky finger and the ulnar half of the ring finger. Patients may also experience pain or a burning sensation that can radiate along the inside of the elbow and forearm. These symptoms frequently worsen when the elbow is held in a flexed position for prolonged periods, such as while sleeping or holding a phone.
As the compression progresses, motor symptoms begin to appear. Individuals may notice weakness in their grip and hand, making common tasks like opening jars or buttoning a shirt difficult. In more advanced cases, muscle wasting, or atrophy, can occur in the small muscles of the hand, particularly those between the thumb and index finger. A visible sign of severe damage is the “ulnar claw,” where the ring and pinky fingers remain slightly bent.
A variety of factors can contribute to ulnar nerve entrapment. Repetitive or prolonged elbow flexion can chronically irritate the nerve. Direct pressure on the elbow, often from leaning on a desk or armrest for extended periods, is another common cause. Other contributing elements include prior elbow fractures or dislocations, the presence of bone spurs, or fluid-filled sacs called ganglia that take up space within the narrow nerve pathways.
Confirming the Diagnosis and Treatment Options
A medical professional will begin the diagnostic process with a thorough physical examination, which includes assessing muscle strength and sensation in the hand and forearm. A specific test often performed is Tinel’s sign, where the doctor gently taps over the ulnar nerve at the elbow to reproduce the tingling sensation in the fingers, helping to localize the site of compression. Other physical maneuvers test for weakness in ulnar-innervated muscles, such as the ability to pinch a piece of paper between the thumb and index finger.
To confirm the diagnosis and determine the location and severity of the compression, objective electrodiagnostic tests are employed. Nerve Conduction Studies (NCS) measure the speed and strength of electrical signals traveling through the ulnar nerve. A significant slowing of the nerve signal across the elbow segment confirms a diagnosis of Cubital Tunnel Syndrome. Electromyography (EMG) involves inserting a thin needle electrode into specific muscles to evaluate their electrical activity, helping to identify signs of chronic nerve injury and muscle damage.
Treatment for ulnar nerve entrapment starts with conservative, non-surgical methods, especially for mild to moderate symptoms. The primary goal is to relieve pressure on the nerve through activity modification, which involves avoiding positions that require prolonged elbow flexion or direct pressure. Night splinting or bracing is often prescribed to keep the elbow straight during sleep, preventing the nerve from being stretched. Physical therapy, including nerve-gliding exercises designed to help the nerve move smoothly through its tunnels, may also be beneficial.
If symptoms persist or if the nerve compression is severe, leading to muscle weakness or atrophy, surgical intervention may be necessary. One common surgical procedure is ulnar nerve decompression, or in situ release, where the constricting tissue around the nerve in the cubital tunnel is cut to create more space. Another option is ulnar nerve anterior transposition, which involves moving the nerve from its location behind the elbow’s bony prominence to a new position in front of it, preventing it from stretching when the elbow is bent. A third procedure, medial epicondylectomy, removes the bony bump at the elbow to relieve pressure on the nerve.